Animals in orbit: why animals live on the International Space Station :: Understanding Animal Research
Ben Madilynn
There is a long history of animals being sent to space. Still today, animals are regular inhabitants of the International Space Station. For twenty years now, the ISS has hosted astronauts conducting scientific research, but also many animal missions coordinated through space agencies including NASA, the European Space Agency (ESA), the Japan Aerospace Exploration Agency (JAXA), and the Russian State Corporation for Space Activities (ROSCOSMOS).
“Animal research in space is either looking at modelling a disease or colonising space. The animal work is helping us understand how to live a better life in space, making it a healthier reality, as well as helping us study a few diseases that affect us down on Earth,” explains Julie Keeble, Director of Biological Services at King’s College London.
Scientists have used their space-flown subjects to study the effects of changes in gravity, radiation and mechanical stress on animal biology and disease. Reduced gravity in space can affect heart and brain function and lead to muscle atrophy or bone loss for instance. The body can also experience sleep disruptions, neuronal changes, premature aging, modulation of the immune system, shifts in the microbiome and how microbes and pathogens interact, and a myriad of other effects. All of these can be studied to understand equivalent conditions on Earth, but also in the hope of mitigating these issues to allow longer and better quality of life in space.
“It is more difficult to study mammalian cells in space than it is on earth and highly specialist systems are required. They don’t fare well in microgravity and away from human care. However, some microorganisms like bacteria, love the microgravity environment. They thrive and couldn’t care less to be left floating around isolated in a module for seven days. As such, a lot of research in space focuses on microorganisms rather than higher species,” explains Dr Keeble.
Different animals have been sent to space and many model organisms have called the ISS home. As on Earth, each species has different advantages and disadvantages from a scientific point of view that make them appropriate for different research questions.
A tiny nematode worm called Caenorhabditis elegans, for example, can fly to space relatively simply in containers akin to “ketchup packets” filled with culture medium and contained within a box about the size of a deck of cards. These can yield thousands of worms, reproducing every few days and maturing on orbit.
“It’s a very cost-effective way of doing experiments in space. Research in space is hugely expensive, reaching tens of thousands of dollars even just for a small module with minimal astronaut interaction. So, the smaller and the less maintenance that they require, the better. Worms are very popular models at the moment for a variety of use ranging from studying composting in space to muscle loss,” says Dr Keeble. “I have myself launched various species into space such as bees or Daphnia water fleas to study pollination, stress, or reproduction in microgravity.”
Zebrafish, Japanese rice fish and Xenopus frog embryos can be kept in a special Aquatic Habitat Unit. Just like worms, flies can be transported in small containers, providing larger numbers of subjects than mice or aquatic species. The fruit fly, Drosophila melanogaster, can be kept within plastic vials containing 60 individuals and some food for the course of the mission. The adult flies can be used to study neurodegeneration or the heart, for example, and can even reproduce while in orbit. Upon their return to Earth, their middle-aged offspring can be used to study signs of dysfunction and remodelling under microgravity.
The only mammals that are still sent to space today are mice. They are an extremely important model for those who want to understand the effects of spaceflight, notably on bone density or muscle atrophy in microgravity.
“The ISS has regularly welcomed rodent missions. However, they demand a lot of planning. Including mice on a space trip has a huge impact on the launch,” explains Dr Keeble. “The mice are launched late onto the rocket, so the maintenance of the mice is very time critical. Everything has to be ready to go on point. It requires a lot of careful planning … and money. For that reason, pharmaceutical companies are the biggest instigators of mice in space, not necessarily to look at whether drugs can work in space, but mostly to model and study diseases. Because of the huge expense related to using mice, there’s a lot more work being done with smaller species.”
Space missions are never taken lightly and have to be carefully designed. There’s hardware and husbandry to think about, and experimental design considerations that minimise astronaut involvement and keep it as simple as possible. Much care and attention goes into designing rodent habitats for the ISS – these aren’t your standard cages – making sure the animals are fed and watered with minimal human intervention.
Mice live in standard research cages until about a week or two before the launch. They are then moved to an environment with a wire bar flooring, which mimics their habitat on the ISS. They are given time to acclimatise to the new flooring that they will encounter in space. Because the mice can float around in microgravity, they need bars to manoeuvre around. The cages are adapted to enable the animals to move around efficiently and cope with different directions of travel.
To avoid floating food, water and waste, mice are given food bars in special containment systems, “cassettes” that can easily be changed by astronauts every two or three days, and provided with water in bags. A low-powered fan behind the cages pulls out and stores the waste. The cages are enriched with small rodent houses that are fixed down, so the mice can hide from view and nest safely. A video system monitors the animals throughout their time in space.
The mice adapt very quickly to microgravity, without demonstrating significant behavioural changes. Some overgrooming can appear, much like when mice are moved into a new environment on Earth. Every detail is observed and recorded by experienced handlers. Prior to going on space missions that involve animal research, every astronaut is trained and certified to handle the animals. “The mice are given priority on the space station,” explains Dr Keeble. “Everything is done to make sure that they’re in the rocket for as little time as possible and in the best possible conditions. Every contingency plan needs to be considered, even one that involves a mouse escaping on board.”
Animals are regular inhabitants of the International Space Station, but the knowledge they reveal doesn’t end in space. Once their mission in microgravity is completed, research animals are brought back down to Earth. “Astronaut vehicles can obviously come back down to Earth, and they bring with them the mice and other experiments, which is fantastic for science. After a few weeks, sometimes months in levitation, the return of the animals is an incredible resource for scientists,” explains Dr Keeble.
Whenever a mission containing biological samples splashes back down, it’s a race against time to retrieve those samples and get them back to the lab before any live animals re-acclimatise to the effects of Earths’ gravity or frozen samples start to thaw. Data is shared among multiple labs to make the most out of each and every animal that is sent to space.
“The amount that is gained from every individual animal is from another planet,” says Dr Keeble. “The preciousness of samples is seen in a whole different light, and each specimen is potentialised. NASA really try to select research proposals that maximise the amount of scientific data retrieved from a cohort of animals. The data is shared among multiple studies and overall reduces the number of animals used.”
In order to make the most of those precious mice, flies, worms and fish, NASA, other international Space Agencies, and others interested in space biology have been on an open-data mission. For scientists such as Dr Keeble the potential of this science is hard to overstate:
“This work is going to change the future of humanity. I think it is so important that a new generation of scientists that is able to understand life in space better, be engaged in space, and there may well be a future population in space.”
Last edited: 3 October 2024 15:52
